The present invention relates to a multicast message communication system and, more particularly, to a limited multicast communication method which can simultaneously transmit an identical message to only a plurality of arbitrarily designated stations and a communication network system realizing the method.
In a local area network, when a message is independently transmitted from a given station to another station, communication is performed using a frame in which an address of a destination station is designated. A station compares the destination address designated in the frame with an address assigned thereto, and when the destination address and the assigned address are the same, the transmitted message is received thereby.
When an identical message is transmitted to all the stations in the network which includes stations having no need transmission of data, a multicast address, which is different from individual destination addresses used in individual message transmission to respective stations, is normally used to transmit the message. All the stations receive the transmitted message when a multicast address is designated in the transmitted frame.
An identical message is often transmitted to a plurality of specified stations connected to a local area network. In this case, conventionally, the message is transmitted using a multicast frame which includes a multicast address mentioned above. With this method, however, data is transmitted not only to necessary stations, but also to unnecessary stations.
Alternatively, the message can be individually transmitted to each of the specified stations with an independent frame. However, with this method, the occupying time of communication lines is increased, thus increasing the load of a network.